A knee-joint orthesis of this type is depicted and described in European Patent Application 705,582. The known knee-joint orthesis has, on both sides of the knee to be supported, two-part rails which in each case terminate with their ends in cup-like fastening means with which the orthesis is attached to the thigh and the lower leg. The two parts of each rail are connected via in each case one hinge, with one hinge (of the inner rail) consisting of one pin, and the other hinge (of the outer rail) consisting of two mutually articulated brackets, which cross one another and are in each case hinged with their one end on the one fastening means and with their other end on the other fastening means.
The principle of connecting two-part rails of a knee-joint orthesis so that they are rotationally movable is based on the recognition that the knee joint executes a rolling and sliding movement. This movement is discussed in a publication by A. Bahler "Die biomechanischen Grundlagen der Orthesenversorgung des Knies" [The biomechanical principles of orthotic fixtures for the knee], Orthopadie-Technik 2/89, pages 52-59. FIG. 6 on page 54 of this publication shows a "compromise pin" as per Nietert, found on the basis of tests discussed in the publication. In this regard, the introduction to the publication states, on page 52, left column, paragraph 1, as follows: The results show that single-pin rails with a 16 mm rearward offset of the pin for medium-sized patients, two-hinge rails with toothing, four-pin hinges and physiological hinges with migrating pin still best satisfy the requirements.
In orthopaedics, a large number of knee-joint ortheses have been proposed which to a greater or lesser extent take account of the above-described findings. Apart from complicated knee-joint ortheses with a multiplicity of bracket and lever connections, which are associated with substantial technical complexity, extensive use is made of ortheses in which their two rail parts are connected only by a single pin. For the optimum configuration of such an orthesis, the position of this pin in relation to the knee joint is crucial. European Patent Specification 393,081 describes a knee-joint orthesis in which on each side of the knee there is in each case a single-pin pivot hinge whose position in relation to two fastening means on the thigh and lower leg is brought about by a displacement of arms attached to the hinges, which arms are provided with a plurality of holes for selective connection to matching pieces attached to the fastening means. By using the holes, the hinges can be advanced to a greater or lesser extent toward the fastening means. This obviously involves a relatively complex mechanism which additionally permits only an incremental adaptation of the position of the pivot hinges to the fastening means.